Fix validation adapter state restore

[bghira]

Summary

• snapshot validation adapter target state before temporary LoRA loading
• prevent teardown from restoring validation adapters that were deleted after generation
• add regression coverage for child-target active adapter state and existing adapter restoration

Tests

• .venv/bin/python -m unittest tests.test_validation_adapters -v
• .venv/bin/python -m unittest tests.test_krea2_model -v
• .venv/bin/python -m unittest -v -f

Fixes #3175